/*
* Copyright (c) 1993, 1994, 1995, 1996, 1997
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that: (1) source code distributions
* retain the above copyright notice and this paragraph in its entirety, (2)
* distributions including binary code include the above copyright notice and
* this paragraph in its entirety in the documentation or other materials
* provided with the distribution, and (3) all advertising materials mentioning
* features or use of this software display the following acknowledgement:
* ``This product includes software developed by the University of California,
* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
* the University nor the names of its contributors may be used to endorse
* or promote products derived from this software without specific prior
* written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*
* pcap-usb-linux-common.h - common code for everything that needs to
* deal with Linux USB captures, whether live or in a capture file;
* the later means that this is *not* Linux-only.
*/
#include <limits.h>
/*
* Return the sum of the two u_int arguments if that sum fits in a u_int,
* and return UINT_MAX otherwise.
*/
static inline u_int
u_int_sum(u_int a, u_int b)
{
return (((b) <= UINT_MAX - (a)) ? (a) + (b) : UINT_MAX);
}
/*
* Is this a completion event for an isochronous transfer?
*/
static inline int
is_isochronous_transfer_completion(const pcap_usb_header_mmapped *hdr)
{
return (hdr->transfer_type == URB_ISOCHRONOUS &&
hdr->event_type == URB_COMPLETE &&
(hdr->endpoint_number & URB_TRANSFER_IN));
}
/*
* Total length of the pseudo-header, including the isochronous
* descriptors.
*/
static inline uint32_t
iso_pseudo_header_len(const pcap_usb_header_mmapped *usb_hdr)
{
return (sizeof(pcap_usb_header_mmapped) +
usb_hdr->ndesc * sizeof (usb_isodesc));
}
/*
* Calculate the packet length for a "this is complete" incoming
* isochronous transfer event.
*
* Calculating that from hdr->urb_len is not correct, because the
* data is not contiguous, and the isochroous descriptors show how
* it's scattered.
*/
static inline u_int
incoming_isochronous_transfer_completed_len(struct pcap_pkthdr *phdr,
const u_char *bp)
{
const pcap_usb_header_mmapped *hdr;
u_int bytes_left;
const usb_isodesc *descs;
u_int pre_truncation_data_len;
/*
* All callers of this routine must ensure that pkth->caplen is
* >= sizeof (pcap_usb_header_mmapped).
*/
bytes_left = phdr->caplen;
bytes_left -= sizeof (pcap_usb_header_mmapped);
/*
* Find the end of the last chunk of data in the buffer
* referred to by the isochronous descriptors; that indicates
* how far into the buffer the data would have gone.
*
* Make sure we don't run past the end of the captured data
* while processing the isochronous descriptors.
*/
pre_truncation_data_len = 0;
for (uint32_t desc = 0;
desc < hdr->ndesc && bytes_left >= sizeof (usb_isodesc);
desc++, bytes_left -= sizeof (usb_isodesc)) {
u_int desc_end;
if (descs[desc].len != 0) {
/*
* Compute the end offset of the data
* for this descriptor, i.e. the offset
* of the byte after the data. Clamp
* the sum at UINT_MAX, so that it fits
* in a u_int.
*/
desc_end = u_int_sum(descs[desc].offset,
descs[desc].len);
if (desc_end > pre_truncation_data_len)
pre_truncation_data_len = desc_end;
}
}
/*
* Return the sum of the total header length (memory-mapped
* header and ISO descriptors) and the data length, clamped
* to UINT_MAX.
*
* We've made sure that the number of descriptors is
* <= USB_MAXDESC, so we know that the total size,
* in bytes, of the descriptors fits in a 32-bit
* integer.
*/
return (u_int_sum(iso_pseudo_header_len(hdr), pre_truncation_data_len));
}
